A. Field of the Invention
The present invention relates to restricting the flow of fluid through an annulus defined by the interior walls of a fluid conduit and the exterior of a tubular member within said fluid conduit. It also relates to a special tool for accomplishing same. In a specific context, it relates to a well packer tool and a method of using same.
B. Description of the Prior Art
It is frequently desired to restrict the flow of fluid through an annulus defined by the interior walls of a fluid conduit and the exterior of a tubular member within said fluid conduit. As used in the preceding sentence, "fluid conduit" includes elongated voids, such as defined by pipes, or by boreholes or mine shafts penetrating the earth, or the like structures having a substantially (i.e., disregarding small cracks, pores, and the like) closed cross sectional perimeter; excluded from the term as used herein are fluid conduits which do not have a completely defined cross section, e.g., an open trough. Examples of situations where such flow restriction is desired in wells include isolating a portion of an annulus between casing and the borehole or between concentric strings of casing or tubing, e.g., during the injection of treating fluids such as water or oil based fluids, acids, cement slurries, sand consolidation slurries and the like.
In the context of mines, it is sometimes necessary to prevent uncontrolled seepage from an overhead aquifer into a mine or water sensitive formation immediately above the mine. One approach to this problem is to insert a drain pipe into an overhead shaft in fluid communication with the aquifer and to seal off the annulus between the drain pipe and shaft so that the water or brine from the aquifer drains through the pipe.
Various tools known as packers have been developed for these purposes. The design and the general nature of a packer may be obtained from text books concerned with well drilling, operation, and reworking. Patents, e.g., U.S. Pat. Nos. 2,567,321; 3,436,084; 3,845,816; 3,135,329; 3,186,489; 3,252,517; 3,454,087; or 3,520,361; or catalogues, e.g., the 1976-'77 edition of "Composite Catalogue of Oil Field Equipment and Service" or "Baker Catalogue for 1960" containing general information on packers presently in use.
A packer is usually positioned and controlled by means of a suspending pipe, tubing, or section, to which it is threaded or otherwise connected. A packer is frequently provided with a laterally movable element having outwardly extending teeth or dogs for engagement with the inner wall of the casing when the packer has been located at the desired level.
In order to provide a fluid-tight seal in the annulus between, for example, a casing and tubing of a wellbore, a deformable rubber cylindrical packer element is usually employed which is relaxed when the packer is open but which, when the packer is to be closed, is mechanically forced axially outwardly, completely closing off the annulus. When the entire wellbore is to be closed off, a centrally positioned plugging member is employed as the packer mandrel instead of open tubing.
Another technique for sealing off an annulus is through use of what has become known in the trade as a chemical seal ring, whereby a fluid, usually a slurry, which sets into a rubberlike gel is injected into the annulus. Shaped articles such as tapes and gaskets have also been prepared from the gels formed from such fluids, inasmuch as the gels imbibe fluids (e.g., aqueous fluids such as water, steam, brines, or acid) and swell. Hence, should there temporarily be any leak about the gel, the gel swells to heal the leak. Use of chemical seal ring material to seal joints in mine shaft and tunnel linings is taught by Taradash et al. in U.S. Pat. Nos. 3,483,706 and 3,504,499. Representative of the chemical ring art are patents by Eilers and Parks, by Pence, Jr., and By Boughton, Pence, Jr., Stude, and Kucera, hereinafter discussed.
In Eilers et al., U.S. Pat. No. 3,306,870, there is disclosed an aqueous-base pumpable sealant composition which forms a gel, and once set, swells upon contact with aqueous fluids. The gel is radially expandable when subjected to compressive pressure. The sealant composition from which the gel is formed comprises an acrylamide type polymer in an aqueous solution of an inorganic compound to reduce the aqueous tension of pure water to certain specified levels. In the teachings of the patent relating to sealing subterranean formations, the gel and resulting seal are formed in situ.
Other compositions are disclosed by Eilers et al. in a series of related patents. U.S. Pat. Nos. 3,839,260; 3,839,262; 3,839,263; 3,845,004 and 3,847,858 are each divisions of U.S. 3,746,725, which is a continuation-in-part of U.S. 3,624,018, which in turn is a continuation-in-part of 3,511,313. All relate to gels formed from a slurry of a particulate, water soluble organic polymer, and an organo solvent therefor. Optionally, the slurry may contain an oxide, hydroxide, or salt of a polyvalent metal, to enhance the properties of the gel. The slurry can be injected into a void space and allowed to set to fill the void.
Similarly, gels prepared from colloidal suspensions of natural or modified natural polymers and certain metal salts are disclosed by Eilers et al. in U.S. 3,611,733.
In U.S. 3,554,287, Eilers et al. disclose a water swellable, resilient solid prepared from an aqueous slurry of certain salts and certain cynthetic polymers.
In U.S. 3,421,584, Eilers et al. prepare gels from water, certain water soluble polymers which are stable at low pH levels, a pH control agent, an acid-stable cross-linking agent, and a sodium silicate.
In U.S. 3,502,149, Pence, Jr. describe gels prepared from certain polymers, a polyhydric compound, water, and a Cr.sup.+6 oxidizing agent. The setting time of such gels can be extended by inclusion of a small amount of cupric ions, as taught in Pence, U.S. 3,677,987.
To control excessive pressure build-up as a result of the gel imbibing fluid, Boughton et al., U.S. 3,593,799 teach means for relieving pressure on the gel once a preselected pressure has been reached.
Finally, a general discussion of the properties of and uses for chemical seal rings is found in "Dowell Chemical Seal Ring and Dowell Chemical Seal Ring Gasket Technical Report", Dowell Division of The Dow Chemical Company form number DWL 1627-6M-868.
The teachings of each of the patents and publications hereinabove discussed are expressly incorporated herein.
While certainly advantageous in its ability to conform to surface irregularities, pumping of a liquid slurry to form a chemical seal ring in situ is sometimes inconvenient, especially where the seal is to be placed overhead.